trouble with converting ATX-300 power supply as bench PSU

Hi all,

As the title says, i have trouble with converting ATX-300 power supply as bench PSU.

There is no more info on this power suppl it say model ATX-300 no brandname or such.

Older version, so it has no on of switch, 20 pins

So, green to GND
Purple and grey have a led with 220ohm resistor.
21 watt car lightbulb as load on 12V rail.

On power up the led on standby lights up, the lightbulb lights op a split second, fan starts turning and stops turning. Any idea what could be wrong here?

Try adding a dummy load to the 5V rail and/or 3.3V rail. Without load it may be tripping on over-voltage, since such
a supply is not designed without expecting substantial 5V/3.3V loads - its perfectly normal for no 12V loads to
be present so that shouldn't trip the supply. The 5V sense is connected to 5V?

Tnx for the reply.

So a load on the 5V. What will pull enough and can i find here laying around in the house.

The 12V car bulb won't work of course, i ordered a 10ohm 25 watt power resistor, guess i'll have to wait till after the hollidays since i dont have any 5V device laying around here :frowning:

Found out with your answer that just a big resistor on the 3.3V was enough to get it up and running! Thanks a million :slight_smile: